Progressive approach osteosynthesis device and preassembly method

ABSTRACT

The present invention relates to an osteosynthesis device, particularly for spinal support or correction, enabling easier and compact implantation, that can be particularly used in the case of implantation via the anterior approach, and a preassembly method for such a device. Said device comprises implants screwed into two vertebrae and one plate characterized in that the plate is joined to at least one implant by attachment structure able to hold said plate without preventing the implant from rotating on its screwing axis, or without preventing a specified clearance of the plate with respect to the implant. In this way, said attachment structure make it possible to continue screwing the implant, or adjust the position of the plate after the plate has been on the implant.

FIELD OF THE INVENTION

The present invention relates to an osteosynthesis device, particularlyfor spinal support or correction, enabling easier and compactimplantation, that can be particularly used in the case of implantationvia the anterior approach, and a preassembly method for such a device.

BACKGROUND OF THE INVENTION

For spinal support or correction, a device comprising one or moresupport bars or plates positioned along the spinal column is used, andfixed to certain vertebrae by implants. Said implants are fixed at oneend to the plate and at the other end to the vertebrae by bone anchoragemeans, for example a threaded part screwed inside the actual vertebra.

In such devices, it is known to use a plate comprising several holes, tojoin the implants fixed to several vertebrae, as described in the patentFR2726171, for example. Said bars then surround or pass through the headof the screw and are locked with a nut screwed onto said head.

However, such a device requires that the implants be fixed andcompletely clamped before the plate is positioned. Therefore, in theevent of delicate operative conditions, it is difficult to successfullyposition the plate very close to the spine. This problem arises forexample when the shape of the spine comprises too many irregularities,due to spinal displacement or deformation or in the presence ofoutgrowths such as osteophytes. There are similar problems in the caseof implantation by the anterior approach, i.e. via the front of the bodyor on the front face of the spine. Indeed, the anatomical conditions inthis case frequently only leave space for a compact size. In addition,it is often necessary to work by means of endoscopy in this case, whichrenders the operation difficult and gives a less satisfactory view ofthe implant insertion depth.

A device according to the prior art also requires that the clamping nutonly be fitted on the screw after the screws and the plate have beenpositioned. Therefore, said nut can only be inserted onto the screw headduring the operation, with all the difficulties and risks of loss thatmay be caused by handling and assembling a small part inside a humanbody. This operation is all the more problematic when said operation isconducted by means of endoscopy, for example when it is necessary toimplant via the anterior approach, i.e. via the front of the body or onthe front face of the spine.

In some cases, to enable subsequent consolidation of the attachmentbetween the implant and the vertebra, an implant composed of a so-called“rehabitable” screw is used, i.e. a hollow screw wherein the insidecommunicates with the outside via openings passing through the threadedwall. During the screwing into the vertebra, part of the bone substancepenetrates inside the screw. Over time, the bone substance fuses betweenthe inside and outside of the screw via these openings, thus forming aconsolidation over time.

In this way, the patent FR 2726171 discloses a hollow screw wherein theopenings are produced by cutting on the inner surfaces of said screwlongitudinal grooves which cut into the base of the outer threading.However, during positioning or subsequently, such a screw may formanchoring which is not sufficiently strong and is liable to be dislodgedor torn from the vertebra wherein it is implanted.

OBJECTS AND GENERAL DESCRIPTION OF THE INVENTION

One of the aims of the invention is to propose a compact osteosynthesisdevice, that can be fitted and adjusted in a position very close to thespine and can also be screwed or clamped when it is not possible to usea tool in the actual axis of the implant.

This aim is achieved by an osteosynthesis device, particularly for thespine, comprising a plurality of implants that can be screwed into oneor more vertebrae and provide a rigid joint between said vertebrae andat least one plate or bar used to hold or displace the spine,characterized in that the plate is joined to at least one implant by anattachment structure able to hold said plate without preventing theimplant from rotating on its screwing axis, or without preventing aspecified clearance of the plate with respect to the implant, or both:thus making it possible to continue screwing the implant, or adjust theposition of the plate, or both, after the plate has been assembled onthe implant, and in that the elongated part, referred to in the instantdrawing as the clamping support 12, of the implant 1 is mobile withrespect to the rest of the implant, along a universal type joint betweena part of the implant referred to as the screw head 102 and a part ofthe clamping support referred to as the support head 122, thus making itpossible to continue screwing the implant after the plate 2 has beenassembled on the implant, by rotating the clamping support around aclamping support axis d12, when said axis d12 forms a non-null angle awith the axis d1 of the implant.

According to an aspect of this invention, there is provided anosteosynthesis device that is adapted to be used in conjunction withsupporting or straitening a spine. The device is an assembly of aplurality of implants that are each adapted to be screwed into at leastone vertebrae. As screwed into a vertebra, each implant is adapted toprovide a rigid support for the implanted vertebrae and a structure thatis made up of at least one plate or bar. The assembly of the plate orbar structure as attached to the several vertebra through the implants,is adapted to hold a spine in place or displace a spine (that is adjustthe shape of the spine).

The plate or bar element(s) is adapted to be joined to at least one saidimplant, that has previously been screwed into a vertebrae is adapted tohold the element in place without impeding further movement of theimplant relative to said vertebra or relative to the supporting element.This attachment structure therefore enables the implant to move aftersaid element has been assembled on the implant.

The implant comprises an elongated structure comprising a support head,that is adapted to be movable with respect to the rest of the implant,and an implant screw head; and an universal joint disposed in operativerelationship between the implant screw head and the support head. Thisstructure enables the implant to be further screwed into the vertebraeafter the element has been assembled on the implant, by rotating theclamping support around a clamping support axis, when the clampingsupport axis forms a non-null angle with the implant axis.

According to one embodiment, at least one implant has an elongated shapearound an axis, referred to as the implant axis, and comprises a firstbone anchoring end bearing at least one threading and a second end withan elongated part passing through a plate support, said plate supportbeing free in rotation around said elongated part, said elongated partbearing clamping means able to hold and clamp the plate against saidplate support.

According to one embodiment, the plate surrounds the clamping support orthe second end of the implant at least partly and rests on a surface ofits complementary plate support, said plate support having on theimplant side a concave surface in the form of a spherical portion whichis supported in a complementary fashion on the outer surface of theimplant screw head.

According to one embodiment, the clamping support has a first elongatedend along the support axis and a second end bearing the support head,said support head having a non-circular cross-section having at leastone concave part and comprising at least one dimension greater than atleast one cross-section of the first end of the clamping support; saidsupport head having firstly one section roughly partly circular along aplane including the support axis, and being secondly arranged in thescrew head inside a housing wherein the inner surface has at least oneprojecting part cooperating with the concave part of the support head toprevent rotation of the clamping support around its axis.

According to one embodiment, the inner surface of the screw head housinghas a shape roughly complementary to the outer surface of the supporthead.

According to one embodiment, the housing receiving the support head has,on the side of said clamping head, a specified dimension to allow theclamping support a clearance along a specified angle, between the axisof the clamping support and the axis of the implant, without saidclamping support escaping from said housing.

According to one embodiment, the clamping support head has a star shapedcross-section with rounded ends, along a plane perpendicular to thesupport axis.

According to one embodiment, the clamping support clamping meanscomprise a threading cooperating with a nut to hold or clamp the plateagainst the plate support.

According to one embodiment, the clamping support comprises at its endopposite the implant an inner or outer recess capable of receiving arotational drive tool and thus enable the screwing or clamping of theimplant in the vertebra.

Another aim of the invention is to propose an osteosynthesis device thatcan be partly preassembled before the operation to enable easierimplantation. Another aim of the invention of the invention is topropose a plate that can be fitted on preassembled implants alreadyscrewed into the spine.

In this way, the invention relates to a device as described above,characterized in that the plate has an elongated shape and comprises onat least one of its ends at least one longitudinally elongated opening,said opening having firstly at least one part opening onto an edge ofthe plate, or one part of a sufficiently large size to be able to beinserted without disassembly in the attachment structure of an implantalready screwed into the spine when said attachment structure arealready assembled, and secondly one part of a roughly constant width andable to slide longitudinally in the attachment structure of said implantafter having been inserted and of being attached thereto; such a platecan thus be assembled by one end to an already fitted implant, and thenslide in the attachment structure of said implant to insert the otherend in another already fitted implant, and then slide again to bringboth ends into the required attachment position, while the attachmentstructure of said two implants were assembled before being fitting ontothe spine.

According to one embodiment, the plate comprises two parts of identicallengths or not, said two parts being joined together by a joining part,said joining part being located in an inner part of the plate, i.e. at asufficient distance from the ends to enable the attachment of the plateonto two implants, at a rate of one implant on either side of saidjoining part.

According to one embodiment, the joining part is located in a positionoffset with respect to the centre of the plate length.

According to one embodiment, the plate has an “H” or “h” shape.

According to one embodiment, the plate has at least one longitudinallyelongated opening, wherein a first region is of constant width and asecond region is larger in size than the first region, said openingbeing able to allow the attachment structure of an implant to passbefore sliding to bring said attachment structure in the first region.

One of the aims of the invention is to propose an osteosynthesis deviceenabling improved screw implantation strength, during fitting, duringthe period prior to bone fusion or after consolidation.

This aim is achieved by a device such as that described above,characterized in that the first bone anchorage end of at least oneimplant has a longitudinal bore concentric to its outer surface, saidbore communicating with the outside by at least one bone fusion openingproduced in the wall between said inner bore and said outer surface,thus enabling a fusion between the inside and the outside of the bonesubstance in contact with said first end.

According to one embodiment, the first bone anchorage end of at leastone implant has two threadings winding in the same direction during thescrewing of the implant, and borne respectively by the outer surface ofsaid first end and the inner surface of the bore that it comprises.

According to one embodiment, at least one bone fusion opening has theshape of a longitudinal oblong hole.

Another aim of the invention is to propose a preassembly method for suchan osteosynthesis device.

This aim is achieved by the preassembly method for a device according tothe invention, characterized in that it comprises the following steps:

-   -   assembly of the plate support on the clamping support of an        implant;    -   assembly of the nut on the threading of the clamping support of        said implant.

BREIF DESCRIPTION OF THE DRAWINGS

The invention, with its characteristics and advantages, will be seenmore clearly upon reading the description with reference to the appendedfigures wherein:

FIGS. 1 a, 1 b, and 1 c represent an osteosynthesis device according tothe invention in an embodiment comprising an “H”-shaped plate and twopolyaxial head implants fitted on an interval vertebra, in threesuccessive phases of the fitting of the plate in the implants;

FIG. 2 represents a longitudinal section view of an implant of a deviceaccording to the invention in the implant clamping phase after insertionof the plate, in an embodiment comprising a plate support free to rotatearound a rehabitable hollow screw implant and fixed clamping support;

FIG. 3 represents a longitudinal section view of an implant of a deviceaccording to the invention in the implant clamping phase after insertionof the plate, in an embodiment comprising a plate support free to rotatearound a rehabitable hollow screw implant and inclinable clamping 5support;

FIG. 3 a represents a partial view of an implant according to theinvention, in a section along a plane passing through the centre of thesupport head and perpendicular to the support axis;

FIG. 4 represents a longitudinal section view of an implant of a deviceaccording to the invention in the plate clamping phase once the implantis in its definitive position, in an embodiment comprising a platesupport free to rotate around a rehabitable hollow screw implant andinclinable clamping support;

FIGS. 5 a, 5 b, 5 c and 5 d represent a top view of a plate of a deviceaccording to the invention, in an embodiment comprising a plate which isrespectively “H”-shaped with two through openings, “h”-shaped with onethrough opening, with two non-through openings and with one non-throughopening;

FIG. 6 represents a side view of an implant of the preassembled deviceaccording to the invention, in an embodiment comprising an inclinableclamping support and a rehabitable hollow screw with two oblong holes;

FIG. 7 a represents a perspective view of a longitudinal section of animplant of a device according to the invention, in an embodimentcomprising an inclinable clamping support and a rehabitable hollow screwwith two oblong holes and according to an alternative embodiment wherethe screw head housing and the support head interact without beingcomplementary in shape;

FIG. 7 b represents a partial perspective view of the support head of animplant of a device according to the invention in the same alternativeembodiment;

FIG. 7 c represents a partial perspective view of a cross-section alongthe plane M of an implant of a device according to the invention in thesame alternative embodiment;

FIG. 8 represents an osteosynthesis device according to the invention inan embodiment comprising an “H”-shaped plate and two polyaxial headimplants according to an alternative embodiment where the implants onlycomprise a single threaded part, on their outer surface.

DETAILED DESCRIPTION OF THE INVENTION

In an embodiment represented in FIG. 2, the device according to theinvention comprises an implant 1 comprising a first end 11 equipped withan outer threading 111, and is illustrated after a first screwing in thebone substance of a vertebra 0, after insertion of a plate 2 and duringthe final approach. Said first end 11 also comprises a cavity or aninner bore, itself equipped with an inner threading 112 wherein thescrewing direction is the same as that of the outer threading 111.During the screwing of the implant into the vertebra 0, part of the bonesubstance tends to fill said cavity and is assisted therein by theaction of the inner threading. Preferentially, the inner threading 112and the outer threading 111 are of the same pitch, so as to minimize thestrain exerted on the bone substance at the entry of the bore duringscrewing.

The wall between the inner cavity and the outside of the implant has oneor more openings, referred to as bone fusion holes 110, in its partwhich is inside the vertebra after the clamping of the implant. In theperiods following the implantation, generally approximately six months,the bone substance present outside and inside the implant tends to fuse.The fusing produced in this way improves the strength of saidimplantation, both by means of blocking via the bone fusion holes 110,and by means of cooperation of the inner threading 112 with the bone pinformed in this way.

In one alternative embodiment, the inner threading 112 has a greaterpitch than that of the outer threading 111. During the screwing of theimplant 1, the bone substance present inside the cavity is thenattracted slightly more quickly than the implant progresses in thevertebra 0. This effect may make it possible to compensate for a fillingdefect liable to occur, for example by compression of the bone substanceinside the bore. This effect may also make it possible to obtain morecomplete or more compact filling of said cavity, for example in order toobtain a specific compression or better filling of the cavity or thebone fusion holes 110, and thus favor bone substance fusion.

At its second end, i.e. opposite the vertebra, the implant 1 comprisesattachment structure used to insert, hold and finally clamp a bar or aplate 2. Said second end also comprises drive means using a tool ofknown type, such as a hexagonal recess 124.

Said attachment structure comprise for example an elongated part 12 ahaving a cross-section less than the central part of the implant,comprising a shoulder Said elongated part 12 a passes through a platesupports resting on said shoulder, and comprises at its end a threading123 adapted to receive a clamping nut 4. In one embodiment, said plate2, FIG. 5 a, is roughly “H”-shaped, comprising for example twocylindrical bars joined at their center by a rigid distance sleeve. Inan alternative embodiment, the two bars are joined by a non-rigid jointenabling more latitude in the positioning of the plate. Said plated isinserted between the plate supports and the nut 4, so as to surround theelongated part 12 a of the implant. Once the plate is in position, thenut 4 is fastened, by hand or using a tool of a known type 52, FIG. 4,and cooperates with the threading 123 to clamp the plate 2 against theplate support 3 and thus lock the attachment.

In said embodiment, the plate support 3 comprises a bore 30 with aroughly rectangular insert passing through its center. Said platesupport 3, on the side of the plate, has one or more roughlycomplementary surfaces 2 to the surface of the plate 2 resting on them.In said embodiment, the central bore of the plate support 3 issufficiently larger than the part 12 a passing through it to allow aclearance of said support 3 transversally and at an angle with respectto the axis d1 of the implant. Said clearance makes it possible toadjust the relative position of the plate supports of two implants 1, 1a easily, and thus insert the plate 2 easily even if the implants arenot well aligned or in the event of a relatively inaccessible anatomicalenvironment. According to an alternative embodiment not shown, the platesupport receives a plate 2 a, FIG. 5 b, comprising a single bar at oneof its ends. Said plate support can then comprise an offset bore insteadof the central bore 30, without leaving the scope of the invention.

Since the plate support 3 is free to rotate around the part 12 a of theimplant 1, it is clearly understood that it is possible to continuescrewing said implant into the vertebra 0, even when the plate isalready in position, provided that the attachment structure are notfastened on said plate 2. In this way, by inserting the plate 2 intosaid attachment structure before the implant 1 is entirely screwed on,it is possible not to be hindered by the various differences in levelsor outgrowths liable to be present in the immediate vicinity of thespine. Once the plate is held in place but not clamped, it is stillpossible to finish screwing the implant into the vertebra, by rotatingthe nut 4 via an opening of the plate supports. The attachment structurethen hold the plate 2 close to the spine, the screwing of the implantproviding sufficient force to oblige the plate to come closer to thespine. Therefore, the plate can be positioned and inserted with littleeffort, while being positioned definitively very close to the surface ofthe vertebra, which makes it possible to obtain a compact device sizeonce fitted.

In a preferential embodiment of the device according to the invention,represented in FIGS. 3, 3 a and 4, the implant 1 comprises a mobilepart, referred to as the clamping support 12, at its second end oppositethe first end 11 screwing into the vertebra 0. Said clamping support 12has an elongated first end 121 along a support axis d12. Said elongatedend passes through the central bore of the plate support 3 and bears athreading 123 30 receiving the clamping nut 4.

At a second end opposite its elongated end 121, the clamping support 12bears a part, referred to as the support head 122, joining said clampingsupport 12 to the implant by its second end, referred to as the screwhead 102, opposite the end 11 screwed into the vertebra 0. Along a planeperpendicular to the support axis d12, said clamping support head 122has at least one dimension s122; FIG. 3 a, greater than at least onecross-section s121 of the elongated end 121 of said clamping support 12.Said support head 122 is retained in a housing provided in the screwhead 102 of the implant 1. For this purpose, said housing has an openingof a specified size s102 so as to retain the support head 122 insidesaid housing, while allowing a clearance of a specified angle a betweenthe support axis d12 and the implant axis d1.

Said angular clearance of the clamping support 12 with respect to theimplant enables angular and lateral movements facilitating to theinsertion of the plate in the attachment structure of the implant, asdescribed below. Said angular clearance also makes it possible tocompensate for any alignment defects between the different implants 1, 1a; FIG. 1 c, of a device according to the invention and thereforerenders the positioning of the plate 2 in the attachment structure ofsaid implants less delicate.

In said preferential embodiment, the plate support 3 rests on the screwhead 102 of the implant 1, by means of a lower surface 31 composing aspherical portion for example. Said lower surface 31 of the platesupport is in complementary contact with an upper surface 13 of saidscrew head. Said spherical complementary contact allows freedom ofrotation and inclination of the plate support 3 with respect to theimplant 1. Said spherical complementary contact of said surfaces 13, 31also enables a uniform and stable support of said surfaces with respectto each other, after the plate 2 has been clamped onto the platesupport, irrespective of the definitive angular position of said platesupport 3 or the clamping support 12.

The implant 1 is screwed into the vertebra 0 by means of a rotationaldrive of said implant by rotating the clamping support 12 around its ownclamping axis d12. Said clamping support is rotated for example by atool, of known type, inserted into at least one recess 124 contained inthe elongated end 121 of said clamping support. The clamping support 12rotates the implant 1 by means of a universal type joint, i.e. therotation of either of the two components around its axis rotates theother component around its own axis, the angle between the two axespossibly being non-null.

Said universal joint is produced by the cooperation of the outer surface120 of the support head 122 with the inner surface 100 of the housing ofthe screw head 102 of the implant 1. Along a plane perpendicular to thesupport axis d12, the support head 12 has a section with a non circularoutline, for example in the shape of a star or cross with roundedcorners, as illustrated in FIG. 3 a. The housing of the screw head 102which receives the support head 122, then has an inner surface 100 inroughly complementary contact with the outer surface 120 of said supporthead 122, said two surfaces 100, 120 cooperating to form the rotationaljoin between these two components 102, 122. The angular variation isallowed by the fact that the support head 122, and its complementaryhousing, have a section with a circular outline along at least one planeincluding the clamping support axis d12, or the implant axis d1, orboth.

According to an alternative embodiment illustrated in FIGS. 7 a to 7 c,the inner surface 100 of the screw head housing receiving the supporthead simply has one or more projecting parts 100 a, for example two. Theouter surface 120 of the support head 122 then has one or more concaveparts 120 a with which the projecting parts 100 a of the screw headhousing cooperate to prevent the rotation of the clamping support 12around its axis d12. In this way, it is clear that it is possible tocontinue screwing the 30 implant 1 into the vertebra 0, while the plate2 is already inserted between the clamping nut 4 and the plate support3, by adjusting the elongated end 121 of the clamping support 12accessible via the nut 4. Since the plate support 3 is free to rotatewith respect to the implant 1, said implant can rotate during screwingwhile leaving the plate 2 and the plate supports immobile.

Once the implant 1 is completely screwed into the vertebra 0, asillustrated in FIG. 4, the plate 2 can then be adjusted and locked inits definitive position, by tightening the clamping nut 4. Said nut maybe tightened by hand, for example on a knurled part of its outer surfaceon the support axis d12, or using a tool 52 of known type, for exampleby adjusting two inner or outer recesses on the nut.

According to an alternative embodiment illustrated in FIG. 8, a deviceaccording to the invention uses such implants but wherein the end 11intended to be anchored in the vertebra only comprises one outerthreaded part 111. In said alternative embodiment, the implant maycomprise a longitudinal bore passing through it from one end to another,to enable positioning by means of sliding around a pin implantedbeforehand in the vertebra. Several implants according to variousalternative embodiments in the same device can of course be combinedwithout leaving the scope of the invention. Depending on theapplications, in order to join two implants 1, 1 a; FIG. 1 c, it ispossible to use a plate of different configurations, for example such asthose represented in FIGS. 5 a, fib, 5 c and 5 d.

In the example of an embodiment illustrated in FIGS. 1 a, 1 b, and 1 c,two implants 1, 1 a are screwed into the body of two vertebrae 0, Oarespectively of the spine, spaced by an interval of one vertebra. Thesetwo implants are then joined together by a plate 2 inserted into theirattachment structure around the clamping support and then clampedbetween the plate support and the nut of each of said implants.

In the preferential embodiment represented in FIG. 5 a, the plate 2 iselongated in shape and comprises two roughly parallel bars 201, 202,which are for example cylindrical, joined together in a rigid orflexible manner by a joining part 20. Said joining part joins the twobars at an inner part of the plate, i.e. at a specified non-nulldistance from each of the ends 21, 22 of the plate. More specifically,said joining part is located at a sufficient distance from each end ofthe plate so that said end can be inserted into the attachment structureof an implant, and possibly slide in said attachment structure. Theposition of said joining part 20 may be located at the center of theplate, or be offset to allow a greater clearance for sliding duringinsertion as explained below.

At each end 21, 22 respectively, of the plate 2, the space between thetwo bars forms an opening 210, 220 respectively, opening out onto theedge of the plate. Said openings have a roughly constant transversal gaps211, s221, enabling longitudinal sliding of the plate in the attachmentstructure of an 15 implant 1, 1 a. This roughly constant transversal gapalso makes it possible to clamp said attachment structure in any part ofsaid openings 210, 220. Since said openings open onto the edge of theplate, it is possible to insert each of the ends of the plate into theattachment structure of an implant 1, 1 a as illustrated in FIG. 1 a,without having to remove the nut 4 if it was preassembled beforehand. Ateach end, this insertion consists of sliding the end of the two barsbetween the nut 4 and the plate support 3 of the implant 1, at eitherside of the clamping support 12.

In another embodiment represented in FIG. 5 b, the plate 2 a iselongated in shape and comprises a first end 21 a comprising a singlebar, which is cylindrical for example. Said first end can be insertedinto an implant according to the prior art or into an implant asdescribed in the present invention, for example in an alternativeembodiment (not shown) where the plate support only comprises a singlesurface 32 in contact with the plate. The plate 2 a also has a secondend 22 a comprising two roughly parallel bars, which are cylindrical forexample. These two bars form a longitudinally elongated opening 220 atogether, of a roughly constant width s221 a. Either of the two ends ofsaid plate 2 a can be inserted, or slide, or both, in the attachmentstructure of an implant according to the invention, in the mannerdescribed in the preferential embodiment.

In another embodiment represented in FIG. 5 c, the plate 2 b iselongated in shape and comprises a first end 21 b having at least oneopening 210 b and a second end 22 b having at least one second opening220 b, at least one of these openings not opening onto the edge of theplate 2 b. These two openings 210 b, 220 b have a longitudinallyelongated 10 shape, i.e. along the length of the plate, and may beseparated by one or more joining parts. These two openings have aroughly constant width s211 b, s221 b, and can be positioned by means ofsliding and then be clamped in the attachment structure of the implants.At least one of said openings has a part, referred to as a notch, of alarger size s210 b, s220 b, of a shape 15 and size able to allow the nut4 of the attachment structure of an implant to pass through. Therefore,such a bar 2 b can also be inserted in the attachment structure of animplant 1 when said attachment structure are already assembled,therefore not requiring handling, in the patient's body, of small partssuch as the nut 4 or the plate support 3.

In an alternative embodiment represented in FIG. 5 d, the plate2 c has asingle opening comprising two notches as described above (see FIG. 5 c).In an embodiment not shown, the plate may comprise a sufficient numberof openings and notches to be able to assemble the plate with more thantwo implants.

It is clear that these different types of openings, which are eitherthrough or have a wider part, can be combined in various ways withoutleaving the scope of the invention.

In the same way, the position of the joining part 20 can vary and beoffset along the length of the plate, so as to leave the clearancerequired for the plate to slide during positioning. In a preferentialembodiment, said position is slightly offset with respect to the centerof the plate, so as to be able to slide the plate sufficiently in thefirst implant 1; FIG. 1 b, to be able to insert it into the secondimplant 1 a.

It is necessary to understand here that the device described can equallywell comprise any other combination of different alternative embodimentsof plates and alternative embodiments of implants without leaving thescope of the invention.

FIGS. 1 a, 1 b, and 1 c illustrate different steps in the positioning ofthe plate 2 in two implants 1, 1 a, in the preferential embodiment. Thispositioning is carried out while the implants are already screwed intothe spine, their attachment structure, in this case the plate support 3and the nut 4, being already assembled on the implant but not clamped.

In this way, in FIG. 1 a, a first end 21 of the plate 2 is inserted inthe attachment structure of the first implant 1, on the plate support 3and under the nut 4, straddled around the clamping support 12.

Once this first end 21 has been inserted, due to the fact that the barshave a roughly constant gap, it is possible to slide the plate in theattachment structure of the first implant 1 until the second end 22 ofthe plate can be aligned (FIG. 1 b) in front of the attachment structureof the second implant 1 a.

By sliding the plate in the opposite direction, it is then possible toinsert (FIG. 1 c) said second end 22 in a similar manner in theattachment structure of the second implant 1 a. It is them possible toadjust the definitive position of the plate 2 and tighten the nut of theattachment structure of each of the two implants, and thus stiffen theassembly. In this way, it is clear that it is possible to prepare theosteosynthesis device in advance using the preassembly method,comprising the following steps:

-   -   assembly of the plate support 3 around the clamping support;    -   assembly of the nut 4 on the threading 123 of the clamping        support.

Once it has been preassembled using this method, an implant 1 of thedevice according to the invention can be used directly during thesurgical operation, as represented in FIG. 6.

The osteosynthesis device can then be positioned using the followingsteps:

-   -   the implants are screwed into the spine, without inserting them        to the ultimate required depth. This approach position makes it        possible not to be hindered by any osteophytes when positioning        the plate 2.

The plate 2 is inserted via a first end 21 into a first implant 1. It isthen slid into said first implant to be presented in front of theattachment structure of the second implant 1 a. The second end 22 isthen inserted into the second implant. This positioning is illustratedin FIGS. 1 a, 1 b, and 1 c.

At this stage and subsequently, the clearance of the plate support 3around the clamping support 12 allows the angular and lateral movementsrequired for insertion. This clearance also makes it possible tocompensate for any alignment defects between the two implants 1, 1 a,and thus renders the positioning of the plate 2 less delicate.

The screwing of the two implants into the spine is then completed untilthey are clamped in their definitive position. This screwing isperformed (FIG. 3) using a tool of known type rotating the implant bymeans of a rotation of the clamping support 12. Since the plate 2 isalready in position and held in place by the attachment structure of theimplants, this additional screwing of the implants drives the plate toits definitive position close to the spine. Therefore, this drivingobtained by screwing the implants makes it 25 possible to reduce thesize determined by said plate, by tightening or inlaying said platefirmly and easily on the surface of the spine.

Once the implants have been completely screwed on, the plate is lockedin the attachment structure of the implants, by clamping (FIG. 4) theirnut 4 on the plate 2 itself resting on the plate support 3 which restson the shoulder or on the screw head 102 of the implant. Naturally, saidclamping may be carried out using other parts not mentioned, such aswashers or locking devices of known types.

It must be clear to those skilled in the art that the present inventionenables other embodiments in numerous other specific forms withoutleaving the scope of the invention as claimed. As a result, the presentembodiments must be considered as illustrations, but may be modified inthe field defined by the scope of the fixed claims, and the inventionmust not be restricted to the details given above.

1. An osteosynthesis device comprising: a plate and a plurality ofimplants, each of the implants comprising a bone anchor having alongitudinal implant axis and a screw head, a clamping support having alongitudinal clamping support axis and comprising a support head, adrive coupler configured for connection to a drive tool, a platesupport, and a clamp, a universal joint coupling the bone anchor and theclamping support and being configured for transmission of a rotation ofthe clamping support around its longitudinal clamping support axisimparted at the drive coupler to a rotation of the bone anchor aroundits longitudinal implant axis while an angle between the implant axisand the clamping support axis is non-zero, and the clamping supportbeing configured to permit said transmission while the plate is attachedto the implant.
 2. The osteosynthesis device of claim 1, in which thebone anchor further comprises a threaded portion disposed along anexternal surface of the bone anchor and configured for screwing into abone.
 3. The osteosynthesis device of claim 2, in which the bone anchorfurther comprises a threaded portion disposed along a hollow core thathas a bone-fusion opening.
 4. The osteosynthesis device of claim 1, inwhich the plate comprises a cylindrical bar and the plate supportcomprises a partially cylindrical surface complementary to the surfaceof the bar.
 5. The osteosynthesis device of claim 1, in which theclamping support is elongated and has first and second distal ends alongits clamping support axis, with the support head disposed at the firstdistal end and the drive coupler disposed at the second distal end. 6.The osteosynthesis device of claim 1, in which the drive couplercomprises a hexagonal recess and the clamp comprises a nut.
 7. Theosteosynthesis device of claim 1, in which the plate support comprisesan opening configured for rotatable disposition of the plate supportabout the clamping support axis.
 8. The osteosynthesis device of claim1, in which the plate support and the screw head have complementarysurfaces configured for support of the plate support by the screw head.9. The osteosynthesis device of claim 8, in which the complementarysurfaces are partially spherical.
 10. The osteosynthesis device of claim1, in which the screw head comprises a housing in which the support headis disposed, and the screw head has a projection configured to cooperatewith a concave portion of the support head to prevent rotation, relativeto the bone anchor, of the clamping support around its clamping supportaxis.